Quiz and Survey Master <= 7.0.1 - Arbitrary File Upload

2020-08-29 00:00
Jerome Bruandet

Strategic Overview

Status
Patched in 7.0.2
Affected Plugin
Quiz and Survey Master (QSM) – Quiz Maker & Survey Maker
Affected Version
<= 7.0.1
CVSS
9.8Critical
Weakness type
CWE-434 · Unrestricted Upload of File with Dangerous Type
CVE
CVE pending
View all Quiz and Survey Master (QSM) – Quiz Maker & Survey Maker vulnerabilities

At a glance

This record tracks a critical-severity Unrestricted Upload of File with Dangerous Type vulnerability in the Quiz and Survey Master (QSM) WordPress plugin, affecting versions <= 7.0.1. It carries a CVSS score of 9.8 (reachable over the network; low attack complexity; high confidentiality, integrity, availability impact). Exploitation requires no authentication. The issue is fixed in version 7.0.2; sites on affected versions should update now. Disclosed August 2020, reported by Jerome Bruandet.

Vulnerability Overview

The Quiz and Survey Master plugin for WordPress is vulnerable to arbitrary file uploads due to missing filename sanitization in the qsm_upload_image_fd_question() function in versions up to, and including, 7.0.1. This makes it possible for unauthenticated attackers to upload arbitrary files on the affected sites server using a double extension attack method which may make remote code execution possible on sites with a configuration that parse the first extension of a file. This is due to an incomplete fix of CVE-2020-35949.

Technical Analysis

The vector marks this flaw as remotely reachable over the network, with low attack complexity — no special timing or configuration is needed, and no privileges on the target site, and no interaction from a victim user. A successful exploit has high impact on confidentiality, integrity, availability — full site compromise territory.

CWE-434: Unrestricted Upload of File with Dangerous Type

Quiz and Survey Master (QSM) <= 7.0.1 carries this weakness at qsm_upload_image_fd_question(), and reaching it takes a caller who can reach the endpoint. An unrestricted file upload lets a caller store a file whose type or destination the application does not properly constrain.

If an uploaded file lands anywhere the server will execute, the flaw becomes remote code execution and the site should be treated as fully compromised. For Quiz and Survey Master (QSM) the fix is 7.0.2: builds <= 7.0.1 are affected, anything from 7.0.2 onward is not.

Remediation

Update to version 7.0.2, or a newer patched version

How does WordSec protect against this?

The attempt arrives as an ordinary request to Quiz and Survey Master (QSM): WordSec's web application firewall inspects request payloads before WordPress loads them. Classes like this one can leave something behind, so the staged malware scanner is the second half: it looks for dropped files and modified code rather than for the request that created them. None of that substitutes for the fix: Quiz and Survey Master (QSM) 7.0.2 closes this, and updating the plugin is the step that ends it.

  • Firewall
  • Scanner
  • Alerts

External References

https://www.wordfence.com/threat-intel/vulnerabilities/id/26140315-04c7-4056-a570-865cd4ffe85e

Related records

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